1. Field of the Invention
The present invention relates to an emission apparatus and a drive method therefor, and, particularly, to an emission apparatus with an emission area (emission pixel array) having an array of a plurality of current driven type (or current controlled type) emission elements each of which emits light at an appropriate luminance gradation as a current according to emission data is supplied thereto, and a drive method for the same.
2. Description of the Related Art
Recently, there are active studies and developments on emission element type emission apparatuses (emission element type displays) each having an emission area with a matrix array of current driven type emission elements, such as organic electroluminescence devices (organic EL devices), inorganic electroluminescence devices (inorganic EL devices) or light emitting diodes (LEDs), as the next generation display devices to the liquid crystal display apparatus.
Particularly, an emission element type display adopting an active matrix drive system has a very superior feature of being able to become flatter and lighter that it can have a faster display response speed and less dependency on the angle of visibility, can have higher luminance, higher contrast, and higher definition of the display image quality, and need no backlight or light guide plate, as compared with the known liquid crystal display apparatuses. Therefore, there is an expectation that application of such an emission element type display to various electronic devices can be expected.
As such an emission element type displays employing the matrix drive system, there is known an organic EL emission apparatus using organic EL devices as emission elements, which employs a drive system to control the luminance gradation by controlling the current flowing to the emission elements based on a voltage signal.
In this case, at each emission pixel, there are provided a current control thin film transistor which has a gate applied with a voltage signal according to emission data and lets a current having a current value according to the voltage value of the voltage signal flow to an emission element, and a switching thin film transistor which performs switching to supply a voltage signal according to the emission data to the gate of the current controlling thin film transistor.
In such an organic EL emission apparatus which controls the luminance gradation by setting the current value of the current flowing to the emission elements based on the voltage value of the voltage signal applied according to emission data, however, the threshold value in the electric characteristic of the current controlling thin film transistor or the like may change with time. When such a change in threshold value occurs, the current value of the current flowing to the emission element varies even with the same voltage value of the voltage signal to be applied according to emission data, so that the emission luminance of the emission element changes, which may impair the emitting characteristic.